Wettability alteration(WA)is one of the principal challenges of oil wet carbonate reservoirs. During primary migration,oil would be replaced with formation brine which contains many cationic ions such as Ca2+,Mg2+ that would boost calcite or dolomite surface charge to more positive,the amount of positive charge in rock/brine and oil/brine contacts region is high due to high cations concentration in formation brine during oil migration. In practice,after many years of migration process,because of negatively charged oil components,attractive forces will be active thus it would absorb the oil component to the calcite or dolomite surface consequently the wettability would change to oil wet. For more production in water flooding process in tertiary recovery processes,the rock wettability should change to more water wet conditions. Low salinity water injection comprising of SO4 2-,Ca~(2+),Na~+ and Mg~(2+)ions is known as a WA method that by dilution of seawater or other accessible brines. In this study,based on active ions in WA mechanism,variation of them in a baseline seawater shows tangible results for better water wetness in case when monovalent and divalent ions are used. In the experiments,WA of seawater with 3-time sulfate,6-time calcium and magnesium(SW-3S-6C-M),(SW-3S-C-6M),(SW-6S-C-3M),(SW-6S-3C-M),(SW-3S-0C-0M),(SW-0S-3C-0M),(SW-0S-0C-3M)and seawater,the contact angles were measured. The results showed that by increasing the amount of sulfate,WA always seems to tend to be more water wet. As for calcite at low temperature in the presence of sulfate the WA happened while no change was noted in the absence of sulfate. Magnesium seemed to have an impact at elevated temperatures and in this case SW-3S-C-6M showed best(from 129° to 30°)in comparison with other brines. Finally,it was found that without refreshing the brine in each step,the results were not appreciable.
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